CCL19 and melanoma: As described above, CCR7 is one driver of NK cell homing to secondary lymphoid tissue under steady state or pathological conditions.131 The frequency of CCR7+ CD56bright NK cells in peripheral blood and the serum concentration of the CCR7 ligand, CCL19, are significantly higher in patients with phase IV melanoma compared to those with stage III melanoma or healthy people.185 Such an increase in serum CCL19 may reduce NK cell migration to melanoma-infiltrated LNs.